Introduction Over the past decade, endovascular techniques for the treatment of acute ischemic stroke have emerged significantly. However, revascularization rates are limited at approximately 80%, and mechanical thrombectomy procedures still last about 1 h. Therefore, we investigated the novel direct aspiration first pass technique for its efficacy and safety.
Methods Our neurointerventional database was screened for patients who received mechanical thrombectomy for acute ischemic stroke using the Penumbra 5MAX ACE aspiration catheter on an intention to treat basis between November 2013 and June 2014. Procedural data, including modified Thrombolysis in Cerebral Infarction (mTICI) score, procedural timings, and complications, as well as clinical data at admission and discharge, were analyzed.
Results 54 patients received mechanical thrombectomy using the 5MAX ACE. Median age was 69 (39–94) years (54% were men). Baseline National Institutes of Health Stroke Scale (NIHSS) score was 15 (2–27) and 44/54 (81%) patients received intravenous thrombolysis. Vessel occlusion sites were 91% anterior circulation and 9% posterior circulation. A successful revascularization result (mTICI ≥2b) was achieved in 93% of cases whereas direct aspiration alone was successful in 30/54 (56%) cases; among these, median time from groin puncture to revascularization was 30 min (9–113). Symptomatic intracranial hemorrhage occurred in 2/54 (4%) patients, and embolization to new territories in 3/54 (6%). Median NIHSS at discharge was 6 (0–24); 46% of patients were independent at discharge.
Conclusions The direct aspiration first pass technique proofed to be fast, effective, and safe. Promising revascularization results can be achieved quickly in more than 50% of patients using this technique as the firstline option. Nevertheless, stent retrievers are still warranted in approximately 40% of cases to achieve a favorable revascularization result.
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For many years, intravenous thrombolysis (IVT) has been the standard of care for acute ischemic stroke within 4.5 h after symptom onset.1 However, IVT is less effective in large artery occlusions, and efficient revascularization is a prerequisite for a favorable clinical outcome.2–4 Therefore, endovascular therapy (EVT) has been developed and has emerged significantly over time.5–9 Recently, miscellaneous stent retrievers have been launched yielding high revascularization rates and approximately 40% favorable outcome rates at 90 days.7 ,10 Large randomized trials published in 2013 could not find significant differences between IVT and EVT in terms of favorable outcome at 90 days; one major criticism was the very low rate of stent retriever based thrombectomies in these cohorts.11 ,12 A new generation of large easy to track aspiration catheters might be the game changer, helping EVT to become the standard of care in acute ischemic stroke with underlying large artery occlusions. Promising results regarding revascularization success, duration of procedure, and high rates of favorable clinical outcome at 90 days have been published recently.13 ,14
The aim of this study was to investigate the Penumbra 5MAX ACE aspiration catheter (Penumbra Inc, Alameda, California, USA) in terms of revascularization efficacy, duration of thrombectomy procedure, complications, and early clinical outcome at discharge.
We conducted a retrospective study comprising all patients who received EVT between November 2013 and June 2014 with the Penumbra 5MAX ACE, in the first instance, at a European stroke center. According to the guidelines of the local ethics committee, no approval was necessary.
Inclusion criteria were large artery occlusion within the anterior or posterior circulation; no age limit; and baseline National Institutes of Health Stroke Scale (NIHSS) score of ≥5 or aphasia if NIHSS was <5 at admission. Patients were eligible for EVT within a time frame from symptom onset to treatment of ≤8 h. If time from symptom onset to admission was uncertain, patients were eligible for EVT when salvageable brain parenchyma was depicted by perfusion CT mismatch.15 ,16
All patients received IVT when eligible, according to the guidelines of the German Society of Neurology. Exclusion criteria were any intracranial hemorrhage and a cerebral infarction of a third or more of the middle cerebral artery (MCA) territory.
Imaging and clinical assessment
All angiographic images were re-evaluated according to the recommendations of the Cerebral Angiographic Grading collaborators, including the target artery lesion, target downstream territory, and modified Thrombolysis in Cerebral Infarction (mTICI) scale, before and after the procedure, as described previously.17 A control CT scan was performed 24 h after intervention or after clinical deterioration to rule out any intracranial hemorrhage. Image evaluation was performed by an experienced interventional neuroradiologist (AM) who was blinded to all of the clinical data. A favorable revascularization result was defined as mTICI ≥2b. Procedural timings were taken from the angiographic records. NIHSS and modified Rankin Scale (mRS) at admission and discharge were assessed by a consultant neurologist.
EVT was carried out as described previously.8 ,13 ,14 In brief, usually a large guide catheter (Penumbra Neuron 088 Max) was placed distally into the internal carotid artery or into the V2 segment of the vertebral artery followed by the aspiration catheter (Penumbra 5MAX ACE) which was advanced to the level of the occlusion, usually over a microcatheter and a microguidewire. After the microguidewire and microcatheter were removed, aspiration was carried out using the Penumbra aspiration pump in all cases. When aspiration alone did not result in successful revascularization, a stent retriever (Penumbra Separator 3D) was added in concert with lesional aspiration through the 5MAX ACE.
Continuous study parameters were compared between patients using either the Welch t test for normally distributed data or the Mann–Whitney U test for non-normally or ordinal distributed data. Fisher's exact test was used for categorical variables. All statistical analyses were performed using Graph Pad Prism V.6.1 (Graphpad Software, La Jolla, California, USA); significance was set at α=0.05.
We identified 54 patients who received EVT with the Penumbra 5MAX ACE in the first instance. Median age of the patients was 69 (39–94) years; 54% were men. Forty-four of 54 (81%) patients received IVT. Baseline NIHSS score was 15 (2–27) and median time from symptom onset to revascularization was 220 min (133–563). Sites of occlusion were: anterior circulation in 91% of cases with MCA M1 in 21/54 (39%), MCA M2 in 14/54 (26%), carotid T and carotid L in 12/54 (22%), and distal internal carotid artery in 2/54 (4%). Within the posterior circulation, occlusions were located at the basilar artery in 4/54 (7%) and in the posterior cerebral artery P1 segment in 1/54 (2%) case. There was no statistically significant difference between those patients who were treated by a direct aspiration first pass technique (ADAPT) alone compared with those who received treatment with an additional stent retriever in terms of their baseline characteristics (table 1).
Pretreatment mTICI score was 0 or 1 in all cases, with mTICI being 0 in 50/54 (93%) cases. A final revascularization result of mTICI ≥2b was achieved in 93% of cases (table 2). ADAPT alone was successful in 30/54 cases (56%) with a median of 1.5 (1–4) aspiration attempts (figure 1); in these cases, successful revascularization (mTICI ≥2b) was achieved in 97% of occlusions. In 24/54 cases (35%), the Separator 3D was used after direct aspiration failed to achieve a sufficient revascularization result after a median of three aspiration attempts, finally resulting in a rate of 88% mTICI ≥2b revascularizations (table 2).
In those 30 cases that were successfully recanalized with the ADAPT technique alone, a rate of 73% mTICI 3 was achieved compared with 54% mTICI 3 when a stent retriever was introduced. Of the 73% mTICI 3 results that were achieved using the ADAPT technique, 14/22 (64%) were achieved after one pass. In the majority of cases first pass aspiration was successful when the occlusion was located at the level of the MCA (10/14, 71%).
Regarding the time from groin puncture to revascularization, there was a highly significant difference between both groups, favoring the direct aspiration alone subgroup (30 min vs 65 min, p=0.0004). We could not find significant differences between the groups regarding the rate of complications or early clinical outcome, although there was a higher rate of independent patients in the aspiration only group (53% vs 38%) (table 2). When comparing patients with a good clinical outcome (mRS ≤2) versus patients with a poor clinical outcome (mRS ≥2) at discharge, we found only baseline NIHSS to be significantly different in both groups (p<0.0001). No other factor was found to differ significantly between the groups. However, within the group of patients with a favorable clinical outcome, a higher number (64% vs 49%) were treated with the ADAPT technique (table 4). The mortality rate was seven times higher in the group that received treatment with aspiration and an additional stent retriever (3%. vs 21%) but this difference was not statistically significant.
The general concept of aspiration thrombectomy has been used previously, but for several reasons this technique did not achieve satisfying results in the past.18 ,19 ADAPT is a novel technique utilizing an atraumatic large bore aspiration catheter that is easily trackable. ADAPT with 5MAX ACE has been reported to achieve mTICI ≥2b rates of 78% when used primarily alone and mTICI ≥2 rates of 95% when adjunctive devices were introduced.14 In addition, ADAPT allows for short interventions; a median duration of 37 min has been reported in the ADAPT FAST study.14 When comparing our results with other recently published trials, we found the rate of mTICI ≥2b results to be comparatively low when ADAPT was used alone (table 3). Compared with the final revascularization rates in ADAPT FAST, our results are comparable; they are considerably higher than the reported rates obtained from large stent retriever registries (93% vs 73–81%; table 3).7 ,9 ,20–22 One reason for the relatively low number of patients (56%) that were successfully recanalized with ADAPT alone in our series could be the sample size, leading to a relatively high impact of a single case. Furthermore, there may have been operator related differences in the number of attempts performed before adding the Separator 3D, especially in terms of previous experience using stent retrievers as first line agents, and in the decisions involved in abandoning established interventional techniques. In this context, it should be noted that all four members of our interventional team had broad experience in endovascular stroke therapy (>300 stent retriever cases since 2010) and all were very familiar with the use of stent retrievers.
From our point of view, we need to discuss whether the additional use of a stent retriever should be defined as rescue therapy of the ADAPT technique. Technically, any stent retriever can be introduced easily through the 5MAX ACE and used immediately in conjunction with lesional aspiration; the system is then versatile enough to treat more resistant clots. The key message here is that more than 50% of patients can be successfully recanalized to mTICI 3 faster than by conventional approaches. A first pass mTICI 3 result was most likely when the occlusion was located at the level of the MCA (10/14, 71%).
Our current median time from groin puncture to final revascularization of 41 min is faster than that reported in stent retriever firstline approaches.9 ,22 Complication rates in our series were comparable with data from most thrombectomy studies investigating stent retriever approaches23 (table 3). Regarding clinical outcome, we found a 46% favorable outcome (mRS ≤2) at discharge, which is outstanding compared with results published to date.7 ,10 ,13 ,14 Nevertheless, this study could not proof an effect of the treatment modality (ADAPT vs additional use of a stent retriever) regarding clinical outcome at discharge, although the rate of patients treated by ADAPT was higher in the group with a favorable clinical outcome (table 4).
Our conclusions are limited by the missing 90 day follow-up in our series and have to be validated in large, randomized, prospective trials comparing both approaches. In light of the limited number of patients and the retrospective nature of the analysis, the results have to be interpreted with caution; angiographic data were self-reported and may be less favorable after core laboratory adjudication.
The direct aspiration first pass technique proved to be fast, effective, and safe; in a considerable number of cases (44% in this study) the additional use of a stent retriever may be necessary to achieve favorable revascularization results. Future trials are mandatory to investigate clinical outcome after direct aspiration thrombectomy.
DB and WW contributed equally.
DB, AW, AK, AM, and WW changed departments in 2014, and had been part of the Department of Radiology and Neuroradiology, Klinikum Vest, Recklinghausen, where the patients were treated.
Contributors All authors made substantial contributions to the conception or design of the work, or the acquisition, analysis, or interpretation of the data for the work; drafting the work or revising it critically for important intellectual content; final approval of the version to be published; and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Competing interests AK and DB received minor speaking honoraria and travel grants from Penumbra. AM and WW are consultants for Penumbra.
Provenance and peer review Not commissioned; externally peer reviewed.